Abstract

Cytoplasmic filaments of indefinite length and approximately 10 nm in diameter are present in many eucaryotic cells. They are called intermediate filaments (IFs) because they are intermediate in diameter between microtubules (20–26 nm) and actin microfilaments (5–6 nm). The IFs are major structural components of neural tissue, where they form bundles called neurofibrils and glial fibrils at the light microscopy level. Astroglial cells accumulate filaments as a basic reaction to injury (fibrous gliosis), and the same is true for neurons under certain pathological conditions including Alzheimer’s senile dementia (neurofibrillary tangles).